ADU Architectural Design Cost: Sacramento Region 2026 Guide

Quick Answer

Design fees for an ADU in the Sacramento region run from $0, if your lot qualifies for a city's free pre-approved plan, up to $22,000 or more for a fully custom design from an independent architect. Most homeowners land somewhere in between: $4,500-$10,000 for a licensed building designer or a design-build contractor's in-house team. Here's the fact that changes that math for a lot of projects and rarely gets explained correctly: California law does not require a licensed architect for most ADUs. Business and Professions Code Section 5537 exempts single-family structures, and appurtenant buildings like garages, from the Architects Practice Act as long as they're woodframe and no taller than two stories plus a basement. Add stamped structural engineering ($1,800-$9,000, more for two-story or difficult soil), a Title 24 energy compliance report ($500-$1,200), and city plan check fees, and the full pre-construction design picture comes into focus. Run the ADU cost calculator for a construction range once your design direction is set, or call (530) 204-8294 to talk through your lot.

The Question That Costs People Money

Ask five different design firms in this region for an ADU quote and you'll get five different starting numbers, and a fair number of them will assume you need an architect before you've said a word about your project. Some do. Most don't.

That distinction is worth nailing down before you sign anything, because it's not a matter of opinion or sales pitch. It's written into state law, and the law is specific enough to check against your actual project. We're a licensed general contractor working design-build ADU projects across this region, not a law firm, so what follows is the statute itself, read directly, plus the practical cost tiers that follow from it.

One honest note up front: we're licensed statewide in California (Lic. #1066117) with over 20 years of construction experience, and we have a project manager working the Sacramento and Davis area directly. We're not going to pretend we've been pulling permits here for decades, because we haven't. What we can do is show you the actual rule and the actual numbers, sourced from the code itself, not a recycled blog summary.

Who Can Legally Draw Your ADU Plans

Start with the statute. Business and Professions Code Section 5537, part of the Architects Practice Act, reads in relevant part:

"This chapter does not prohibit any person from preparing plans, drawings, or specifications for any of the following: (1) Single-family dwellings of woodframe construction not more than two stories and basement in height. ... (3) Garages or other structures appurtenant to buildings described under subdivision (a), of woodframe construction not more than two stories and basement in height."

Read that plainly and it says what it looks like it says: for a standard woodframe single-family structure, or a garage or other structure attached to that use, capped at two stories plus a basement, you don't need a licensed architect's stamp to prepare the plans. An accessory dwelling unit is exactly that kind of structure in the overwhelming majority of cases in this region, whether it's a detached unit in the backyard, an attached addition, or a garage conversion.

Subdivision (b) is the part that actually matters for cost planning, because it's where the exemption has a real limit:

"If any portion of any structure exempted by this section deviates from substantial compliance with conventional framing requirements for woodframe construction... the building official having jurisdiction shall require the preparation of plans, drawings, specifications, or calculations for that portion by, or under the responsible control of, a licensed architect or registered engineer."

In plain terms: the exemption covers conventional construction. The moment your design steps outside conventional framing tables, an unusually long span, a large glazed wall, a moment-frame or steel element, an oversized cantilever, that portion needs a stamp from either a licensed architect or a registered structural engineer. The rest of a straightforward ADU can still be drawn by someone who isn't licensed as an architect.

So when is an architect actually required? Generally, in three situations: the ADU isn't woodframe construction (steel or masonry, uncommon but not unheard of on a challenging lot), the design exceeds two stories and a basement, or a specific portion of the design deviates from conventional framing and triggers subdivision (b). Outside those situations, a building designer, a licensed contractor's own designer, or a draftsperson can legally prepare a permit-ready set. If you're close to any of those lines, your city's plan checker makes the final call, not a blog post, so ask early rather than assume.

Want to know which category your project falls into before you commission anything? Call (530) 204-8294 and we'll walk through your lot and your design goals.

Architect vs. Draftsperson vs. Design-Build: The Real Cost Tiers

With the legal question settled, here's what each route actually costs in this region.

Tier 1: Free Pre-Approved City Plans — $0 Design Fee, $1,500-$4,000 Site Adaptation

Three cities in this cluster currently offer live, free pre-approved ADU plan catalogs: Davis (studio ~300 sq ft, one-bedroom ~565 sq ft, two-bedroom ~740 sq ft), the City of Sacramento's Shelf-Ready ADU Plans (367, 559, and 747 sq ft), and Elk Grove (625 sq ft one-bedroom, 745 sq ft two-bedroom). Dixon runs a related model where designers submit plans for city approval on an ongoing basis rather than a fixed size menu. Woodland's catalog is still listed as "coming soon" as of this writing. We covered the full city-by-city status in our pre-approved plans comparison.

The plan itself costs nothing in the cities that have one. What it doesn't include: a site-specific plot plan showing your parcel's exact setbacks and easements, foundation engineering adapted to your soil, utility connection drawings, and a Title 24 report tailored to your specific lot. Budget roughly $1,500-$4,000 for that adaptation work, which is still a fraction of a full custom design fee.

Tier 2: Licensed Building Designer or Draftsperson — $4,500-$10,000

This is the most common route for a standard single-story detached ADU, an attached addition, or a garage conversion in this region. A building designer working under the Section 5537 exemption produces the full permit-ready package: site plan, floor plans, elevations, structural drawings for conventional framing, and coordination on the Title 24 report. You're not paying for an architect's license, but you're getting a complete, code-compliant drawing set.

Tier 3: Licensed Architect — $9,000-$22,000+

Independent architects make sense for a genuinely custom design: a two-story detached unit, a hillside or clay-soil lot requiring close coordination between the design and the geotechnical work, an unconventional footprint, or a case where a homeowner's association or a city's design-review process wants a specific architectural style matched to the primary house. Two-story detached ADUs, which we covered in detail in a separate height-rules guide, are still generally exempt under Section 5537 as long as they stay woodframe and inside the two-story-plus-basement cap, but the added structural complexity of a second story often pushes homeowners toward an architect anyway for the coordination alone, not because the law requires it.

Tier 4: Design-Build — $0-$4,000 Separate Fee

With a design-build contractor, design work is generally folded into the overall construction contract rather than billed as a standalone architectural fee. This is the model we use. It doesn't remove any of the legal requirements above, structural calculations still get stamped when they deviate from conventional framing, and Title 24 compliance is still required, but it collapses the coordination between designer and builder into a single point of contact, which tends to reduce both cost and schedule friction.

Run the ADU cost calculator to see how design fees fit into a full project budget, or call (530) 204-8294 to talk through which tier makes sense for your lot.

Structural Engineering and Title 24: The Two Costs Almost Every Tier Shares

Regardless of who draws your floor plans, two cost lines apply to nearly every ADU in this region.

Stamped structural engineering. California's civil and structural engineers are licensed separately from architects, under their own practice act, through the state's Board for Professional Engineers, Land Surveyors, and Geologists. Their stamp is what Section 5537(b) requires the moment a design steps outside conventional framing tables, and it's also standard practice for foundation design on most ADUs regardless of whether the framing itself is conventional. A straightforward single-story, slab-on-grade ADU with conventional wood framing typically runs $1,800-$5,000 for structural calculations. A two-story detached unit, a hillside lot, or a site with expansive clay soil, which shows up in pockets throughout this region and can require deeper or more heavily reinforced footings, pushes that number to roughly $4,000-$9,000. If your lot has known soil challenges, our clay soil foundation guide goes deeper into what that adds to a build.

Title 24 energy compliance. California's Building Energy Efficiency Standards, Title 24 Part 6, require a compliance report showing your ADU meets the state's insulation, window, HVAC, and lighting standards before a permit gets issued. This is a separate requirement from local building codes and applies statewide, not just in this region. Most design packages, whether from a designer, an architect, or a design-build contractor, include this report as part of the fee. If it's billed separately, plan on $500-$1,200 for a standalone Title 24 report prepared by a certified energy consultant or HERS rater.

Neither of these costs disappears if you go the pre-approved-plan route. A free city catalog plan still needs site-specific structural verification for your lot's soil and a Title 24 report matched to your unit's actual specifications, which is exactly why Tier 1 above still carries that $1,500-$4,000 site-adaptation range.

Plan Check: What It Actually Costs, City by City

Plan check is where your design gets tested against the local building code, and fees vary by jurisdiction. Here's what's actually published in this cluster's own permit guides, held consistent rather than re-invented for this post.

City of Sacramento: Budget roughly $1,200-$4,000 for the plan check fee itself, separate from a building permit fee of about $3,500-$9,000 that scales with the project's valuation. Community Development is the department handling ADU review; full detail is in our Sacramento ADU guide.

Davis: Permit and plan-check fees are typically quoted together in Davis, running roughly $7,000-$16,000, which folds in utility-connection-related charges. The City of Davis Building Division, (530) 757-5610, is the direct line for a current number on your specific project. See our Davis ADU guide for the full permit walkthrough.

Elk Grove, Folsom, Woodland, Dixon, Roseville, and West Sacramento each publish their own fee schedules, and we're not going to guess at numbers we haven't independently verified for this specific post. Call the building counter directly, or use the city-specific guides linked at the bottom of this article for what we've verified there.

One detail worth knowing before you assume a fee applies: several cities in this cluster waive impact fees entirely for ADUs under 750 square feet, a state-law protection under SB 543, which can meaningfully change your bottom line depending on unit size.

Pre-Approved vs. Custom: The Decision That Actually Matters

Here's the honest framework, not a sales pitch for either direction.

Pre-approved makes sense when: your lot is flat with no unusual soil conditions, your ADU fits one of the published sizes (Davis's 300/565/740, Sacramento's 367/559/747, or Elk Grove's 625/745), you're not trying to match a specific architectural style to your main house, and speed matters more than customization. Most of the design fee and a large share of the structural plan-check work is already done and pre-accepted by the city, which is the entire value of these programs.

Custom design makes sense when: your lot is sloped or has documented soil challenges, you want a layout, roofline, or exterior style the catalog doesn't offer, you're building a two-story detached unit (not currently covered by any regional pre-approved catalog), or your property sits close to a setback or lot-coverage constraint that a standard footprint won't clear.

There's a middle ground worth naming honestly: adapting a pre-approved plan's general layout while still commissioning custom site-specific engineering can sometimes split the difference on cost, though not every city allows direct plan reuse, and adaptation work still needs its own structural and Title 24 verification for your parcel.

Timeline: Design Through Permit Issuance

Design and engineering timelines vary by route and by city, but here's a realistic range built from the timelines already published across this region's permit guides.

The single biggest schedule risk isn't the design tier you choose. It's an incomplete submittal. A missing site plan, an unsigned form, or a Title 24 package that doesn't match your final floor plan resets the clock, regardless of whether an architect or a designer prepared your drawings.

What This Costs Alongside Construction

Design fees are one line item in a bigger budget. Held consistent with our other regional guides:

These are regional planning ranges, not a quote for your specific lot. Design tier, soil conditions, utility distance, and finish level all move the final number. Get a construction range in about two minutes at the ADU cost calculator, no site visit required, or call (530) 204-8294 to talk through your project.

What We Verified, and What We Didn't

Business and Professions Code Section 5537, including the full text of subdivisions (a)(1), (a)(3), and (b), was read directly at leginfo.legislature.ca.gov, current as amended by Stats. 1996, Chapter 184, effective January 1, 1997, with no more recent amendment found. That's the primary-source basis for everything in this post's "who can legally draw your ADU plans" section, and it's the same statute regardless of which California county you're building in, since it's state law, not a local ordinance.

Design fee ranges, structural engineering costs, and Title 24 costs are our own market-based planning estimates, not published fee schedules, and are labeled as such throughout. Sacramento's plan check and permit fee figures, and Davis's combined permit-and-plan-check figure, are reused directly from our previously published, separately verified city permit guides rather than re-derived here. We did not publish plan check fee figures for Elk Grove, Folsom, Woodland, Dixon, Roseville, or West Sacramento in this post; those numbers belong in each city's own permit guide or at that city's building counter, not guessed at here.

We also did not independently re-verify the exact statutory citation for the Board for Professional Engineers, Land Surveyors, and Geologists' licensing authority for this post; the board's name and general role are stated as well-established public fact, not as a newly sourced legal claim.

How We Work in the Sacramento Region

We're a licensed California general contractor, CA Lic. #1066117, with over 20 years of construction experience across the state and a 5.0-star Google rating. We have a project manager working the Sacramento and Davis region directly. We didn't grow up doing design work in these neighborhoods, and we're not going to write it that way. What we bring is the same read-the-actual-statute approach that went into this guide, applied to your specific lot, plus a design-build process that keeps the coordination between your plans and your construction contract under one roof. Learn more about our work in Sacramento and Davis.

Start With a Real Number

Design fees shouldn't be the mystery line item in your ADU budget. Now you know the actual rule, the actual tiers, and where the real costs sit. Get a construction estimate in about two minutes at the ADU cost calculator, or call (530) 204-8294 and we'll help you figure out which design route actually fits your lot before you sign anything.

Frequently Asked Questions

Safeway Construction — CA Lic. #1066117 | 20+ years of California construction experience | 5.0-star Google rating | Serving Sacramento, Elk Grove, Davis, Folsom, Woodland, West Sacramento, Roseville, and Dixon.

Phone: (530) 204-8294

Related Guides

• Pre-Approved ADU Plans in the Sacramento Region: A 2026 City-by-City Comparison
• Davis Pre-Approved ADU Plans: What They Save and What They Don't (2026)
• Sacramento ADU Guide: Permits, Costs and EZPermit (2026)
• Two-Story Detached ADU Height Rules: Sacramento Region 2026
• ADU Contractor Questions Before Hiring: Sacramento Region 2026